Tag Archives: Sharpless

Sh2-184 NGC281 The Pac-Man Nebula (or, alternately, the Spouting Whale Nebula)

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Sharpless Sh2-184 NGC281 is commonly called the Pac-Man Nebula for obvious reasons – it looks like the video game character Pac-Man with its round shape and open mouth.  Yet I also see a spouting whale – same big mouth but with a tail and spouting water out of its blowhole.  Can you see it?

I made two versions of this – one “square” with the frame that is missing the stars in the upper right corner, and one “surfing the waves” angled one that has a complete starfield.  Which version do you like better?

This image shows HII region Sharpless Sh2-184 (the whole image) and the open cluster IC1590 (stars in the blue region).  

Sh2-184 is an H II region emission nebula, a region of ionized atomic hydrogen.  The H II regions in the Sharpless 2 catalog were “defined not only in terms of the ionized gas but also in terms of the hot stars which are responsible for the ionization.”

The young open cluster IC1590 is about 3.5 – 4.4 million years old.  Among other stars, it contains four O type stars, short-lived, hot, massive stars that ionize the surrounding molecular cloud. 

The massive stars are believed to be triggering star formation in the surrounding H II region by ionizing, heating, and compressing gas in molecular cloud in which they formed.  In the periphery of the open cluster, Young Stellar Objects (YSOs), young, low-mass stars deeply embedded in parent molecular cloud, are found that are 1 – 2 million years old and 0.5 – 3.5 times the mass of our sun.  I am always amazed when I realize that our galaxy is still under construction!

Sh2-184 is located in the Milky Way, approximately 10110 light years away.  This image is 50 arc minutes across, so the image is approximately 150 light years across. 

I collected the frames for this image under the fantastic dark skies of Dell City, Texas.  When we go out there, I generally try for some easier targets and a more difficult target – this was one of the easier targets.  I need far less time than I do for images from my light-polluted driveway, but it was something of a guess to know whether I’d taken enough data to end up with a good image.  In this image, the stars came from images using red-green-blue filters with 30 minutes of data each, and the nebula came from images using Sulfer ii (3.33 hours of data mapped to red), Hydrogen alpha (3.5 hours of data mapped to green) and Oxygen iii (3 hours of data mapped to blue) filters, the standard SHO mapping.  But after doing that mapping, I used Narrowband Normalization to shift the colors so that it wasn’t overly green and to enhance the reds and blues.  The nebula was processed separately from the stars to maximally enhance it.  As always, I like color, so I leaned into the rich colors.

What do you think of the colors?  What do you think of the alternate name?

Camera geek info – Narrowband:

  • William Optics Zenith Star 73 III APO telescope
  • William Optics Flat 73A
  • ZWO 2” Electronic Filter Wheel
  • Antila RGB and SHO filters
  • ZWO ASI183MM-Pro-Mono camera
  • William Optics Uniguide 32MM F/3.75
  • ZWO ASI220MM-mini
  • ZWO ASiair Plus
  • iOptron CEM40
  • Dell City, Texas Bortle 2 – 3 skies

Frames:

  • November 8, 2025
    • 11 300 second Gain 150 Ha lights
    • 30 1 second Gain 150 Ha flats
    • 11 300 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
    • 11 300 second Gain 150 Sii lights
    • 30 1 second Gain 150 Sii flats
  • November 9, 2025
    • 9 300 second Gain 150 Ha lights
    • 30 1 second Gain 150 Ha flats
    • 9 300 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
    • 8 300 second Gain 150 Sii lights
    • 30 1 second Gain 150 Sii flats
  • November 10, 2025
    • 60 30 second Gain 150 Red lights
    • 30 0.05 second Gain 150 Red flats
    • 60 30 second Gain 150 Green lights
    • 30 0.02 second Gain 150 Green flats
    • 60 30 second Gain 150 Blue lights
    • 30 0.02 second Gain 150 Blue flats
  • November 11, 2025
    • 22 300 second Gain 150 Ha lights
    • 30 1 second Gain 150 Ha flats
    • 16 300 second Gain 150 Oiii lights
    • 30 0.5 second Gain 150 Oiii flats
    • 21 300 second Gain 150 Sii lights
    • 30 1 second Gain 150 Sii flats
  • 30 Flat Darks matching flat durations from library
  • 30 Darks matching light durations from library

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXTerminator
  • Narrowband Normalization

Sh2-86 A Lighthouse at Sunset with an Oncoming Storm or, more simply, the Lighthouse Nebula

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Sharpless Sh2-86 does not have a common name, and I think it’s fun to come up with my own names for these objects.  To me, with this framing, the “finger” or “pillar” in the lower center looks like a lighthouse – can you see the beam pointing to the left?  It’s standing on a rocky shore near the blue water (can you see a fish jumping out of water to its right?).  It’s at sunset – the vibrant red to the right – with a storm coming in – the dark spots to the left.  So I call this image “A Lighthouse at Sunset with an Oncoming Storm.” Or, more simply, the Lighthouse Nebula.

This image shows HII region Sharpless Sh2-86 (the whole image), the open cluster NGC6823 (stars in the center of the blue region), and emission nebula NGC6820 (pink spot to the upper left). 

Sh2-86 is an HII region emission nebula, a region of ionized atomic hydrogen.  It is a peak region in a molecular cloud, an interstellar cloud of gas molecules, whose density allows the formation of molecules such as molecular hydrogen (H2) and carbon monoxide (CO).  It is located in the “local spur” region between the “local arm” of the Milky Way where our solar system is located and the “Sagittarius Arm” which is closer to the galactic center.  (There’s a great overhead diagram of our galaxy showing the different arms in A Parallax-Based Distance Estimator for Spiral Arm Sources.)  One theory is that the region is made of three different molecular filaments moving at different velocities, the intersection of which led to the formation of the young open cluster NGC2823.

The young open cluster NGC6823 is about 3 million +/- 1 million years old.  It contains at least 17 OB type stars, short-lived, hot, massive stars that emit UV radiation that ionizes the surrounding molecular cloud.   

Sh2-86 also contains emission nebula NGC6820 which contains an embedded cluster of stars.  

Sh2-86 is located in the Milky Way, approximately 6500 light years away.  This image is 42.2 arc minutes across, so the image is approximately 80 light years across. 

In this image, the stars came from images using red-green-blue filters with a little over 30 minutes of data each, and the nebula came from images using Sulfer ii (4.35 hours of data mapped to red), Hydrogen alpha (3.05 hours of data mapped to green) and Oxygen iii (15.6 hours of data mapped to blue) filters, the standard SHO mapping.  But after doing that mapping, I used Narrowband Normalization to shift the colors so that it wasn’t overly green and to enhance the reds and blues.  The nebula was processed separately from the stars to maximally enhance it.  After making this uber-vibrant version, I tried several rounds of trying to make a more subdued version, but I just didn’t like them as well.  So the vibrant color was an artistic decision.

What do you think of the colors?  What do you think of the name?

Camera geek info – Narrowband:

  • William Optics Pleiades 111 telescope
  • ZWO 2” Electronic Filter Wheel
  • Antila SHO and RGB filters
  • Blue Fireball 360° Camera Angle Adjuster/Rotator
  • ZWO ASI183MM-Pro-Mono camera
  • William Optics Uniguide 32MM F/3.75
  • ZWO ASI220MM-mini
  • ZWO ASiair Plus
  • iOptron CEM40
  • Friendswood, Texas Bortle 7-8 suburban skies

Frames:

  • August 7, 2025
    • 61 180 second Gain 150 Ha lights
    • 30 0.5 second Gain 150 Ha flats
  • August 8, 2025
    • 86 180 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • August 9, 2025
    • 45 180 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • August 14, 2025
    • 77 180 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • August 16, 2025
    • 86 180 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • August 24, 2025
    • 7 180 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
    • 100 20 second Gain 150 Red lights
    • 30 0.02 second Gain 150 Red flats
    • 99 20 second Gain 150 Green lights
    • 30 0.01 second Gain 150 Green flats
    • 96 20 second Gain 150 Blue lights
    • 30 0.01 second Gain 150 Blue flats
  • September 4, 2025
    • 69 180 second Gain 150 Sii lights
    • 30 0.5 second Gain 150 Sii flats
  • November 25, 2025
    • 8 180 second Gain 150 Sii lights
    • 30 0.5 second Gain 150 Sii flats
    • 1 180 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • November 26, 2025
    • 10 180 second Gain 150 Sii lights
    • 30 0.5 second Gain 150 Sii flats
    • 10 180 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • 30 Flat Darks matching flat durations from library
  • 30 Darks matching light durations from library

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXTerminator
  • Narrowband Normalization

NGC7635 The Bubble Nebula

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NGC7635, or the Bubble Nebula, consists of an emission nebula numbered Sharpless Sh2-162 surrounding a bubble surrounding a massive young type O star.  The emission nebula Sh2-162 is part of a molecular cloud, an interstellar cloud of gas molecules, whose density allows the formation of molecules such as molecular hydrogen (H2) and carbon monoxide (CO).  The source of energy creating the bubble and lighting up the emission nebula is the young, hot, type O star BD+60 2522.  The star is about 27 +/- 7 times the mass of the sun and 2 million years old.  The bubble is estimated to only be about 50,000 years old and is striking for appearing nearly spherical and for its star not being near its geometric center (in this image, the star is the bright white circle to the left underneath the bright white arc on the bubble’s surface).  The bubble was created by the solar wind from the star pushing the material around it into a thin, dense shell.  I found a paper from 2019 that argues that because the star is moving at a relatively high velocity and the bubble is relatively young, the star is creating a bow shock.  If the bow shock is the case, the bubble is probably closer to us than the emission nebula and moving towards it.  The bubble and nebula being significantly brighter on one side (the left side in this image) could be explained either by the bow shock or by the interstellar matter on that side being denser.  

The Bubble Nebula is located in the Milky Way, approximately 8155 light years away.  The nebula has an apparent size of 0.69 degrees, so it is approximately 99 light years across.  The bubble itself is about 3 arc-minutes in diameter, so it is approximately 7 light years across.

In this image, the stars came from images using red-green-blue filters with 12 to 33 minutes of data each, and the nebula came from images using Sulfer ii (7.4 hours of data mapped to red), Hydrogen alpha (2.8 hours of data mapped to green) and Oxygen iii (8.1 hours of data mapped to blue) filters, the standard SHO mapping.  But after doing that mapping, I used Narrowband Normalization to shift the colors so that it wasn’t overly green and to enhance the reds and blues.  This tool made getting the colors in this nebula look good a lot easier!  The nebula was processed separately from the stars to maximally enhance it.

I think this nebula is stunning!  We live in a universe filled with wonders.

Camera geek info – Narrowband:

  • William Optics Pleiades 111 telescope
  • ZWO 2” Electronic Filter Wheel
  • Antila SHO and RGB filters
  • Blue Fireball 360° Camera Angle Adjuster/Rotator
  • ZWO ASI183MM-Pro-Mono camera
  • William Optics Uniguide 32MM F/3.75
  • ZWO ASI220MM-mini
  • ZWO ASiair Plus
  • iOptron CEM40
  • Friendswood, Texas Bortle 7-8 suburban skies

Frames:

  • August 7, 2025
    • 56 180 second Gain 150 Ha lights
    • 30 0.5 second Gain 150 Ha flats
  • August 8, 2025
    • 4 180 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • August 14, 2025
    • 31 180 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • August 16, 2025
    • 42 180 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • September 4, 2025
    • 50 180 second Gain 150 Sii lights
    • 30 0.5 second Gain 150 Sii flats
  • September 11, 2025
    • 55 180 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
  • September 12, 2025
    • 65 180 second Gain 150 Sii lights
    • 30 0.5 second Gain 150 Sii flats
  • September 13, 2025
    • 100 20 second Gain 150 Red lights
    • 30 0.02 second Gain 150 Red flats
    • 35 20 second Gain 150 Green lights
    • 30 0.01 second Gain 150 Green flats
    • 51 20 second Gain 150 Blue lights
    • 30 0.01 second Gain 150 Blue flats
  • October 25, 2025
    • 30 180 second Gain 150 Oiii lights
    • 30 0.2 second Gain 150 Oiii flats
    • 33 180 second Gain 150 Sii lights
    • 30 0.5 second Gain 150 Sii flats
  • 30 Flat Darks matching flat durations from library
  • 30 Darks matching light durations from library

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXTerminator
  • Narrowband Normalization

Sh2-188 Dolphin Nebula or Shrimp Nebula

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Sh2-188 is one of the dimmer objects that I imaged during our recent trip to the dark skies at Dell City, Texas.  

Sh2-188, also called the Dolphin Nebula or Shrimp Nebula, is a planetary nebula – the gases expelled from a star before it becomes a white dwarf, lit up by that star.  It’s located in the Milky Way, approximately 2770 light years away, and it’s approximately 8.2 light-years across, giving it an apparent size of 10 arcminutes.  It’s estimated to be 22,500 years old.  

The nebula’s bow shape (as opposed to a circular shape) is theorized to be due to its relatively high velocity interaction with the interstellar medium.

The objects in our galaxy never cease to amaze me!

Camera geek info:

  • Canon EOS 60D in manual mode, 3 minute exposure, ISO 2000
  • Intervalometer
  • Williams Optics Zenith Star 73 III APO telescope
  • Williams Optics Flat 73A
  • iOptron CEM40
  • Dell City, Texas Bortle 2-3 dark skies

Frames:

  • October 9, 2023 
    • Run 1
      • 59 3 minute lights 
      • 30 0.01 second flats
      • 30 0.01 second flat darks
    • Run 2
      • 76 3 minute lights 
      • 30 1/400 second flats
      • 30 1/400 second flat darks
    • 17 3 minute darks

Processing geek info:

  • PixInsight
  • BlurXterminator
  • NoiseXterminator
  • StarXTerminator
  • Generalized Hyperbolic Stretch